SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



FAKT OF VOLUME XXXIV 



On the Construction of a Silvered Glass 

 Telescope, Fifteen and a Half Inches 

 IN Aperture, and its Use in Celes- 

 tial Photography 



By henry draper, M.D. . 



PROFESSOR OF NATURAL SCIENCE IN THE UNIVERSITY OF NEW YORK 

 (Reprinted from Vol. XI\ , " Smithsonian Contributions to Knowledge," 1864) 



AND 



On the Modern Reflecting Telescope 



AND THE Making and Testing 



OF Optical Mirrors 



By GEORGE W. RITCHEY 



ASSISTANT PROFESSOR OF PRACTICAL ASTRONOMY, AND SUPERIN 1 ENDENT OF 

 INSTRUMENT CONSTRUCTION, IN VERKES OBSERVATORY 



(No. 1459) 



CITY OF WASHINGTON 

 PUBLISHED BY THE SMITHSONIAN INSTITUTION 



1904 



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